Diaphragm pumps are widely used, particularly for pumping liquids, solutions, viscous materials, slurries, suspensions, or flowable solids. Such pumps, particularly double diaphragm pumps of the type disclosed in U.S. Pat. No. 3,782,863 and 4,472,115 are well known for their utility in pumping viscous or solids laden liquids, as well as for pumping plain water or other liquids, and high or low viscosity solutions based on such liquids. Accordingly, such double diaphragm pumps have found extensive use in pumping out sumps, shafts, and pits, and generally inhaling a great variety of slurries, sludges, and waste-laden liquids. Fluid driven diaphragm pumps offer certain further advantages and convenience, effectiveness, portability, and safety. Double diaphragm pumps are rugged and compact and, to gain maximum flexibility, are often served by a single intake line and deliver liquid through a short manifold to a single discharge line.
In such pumping apparatus, a diaphragm forming a movable wall of a pumping chamber is moved in a suction stroke to draw liquid into the pumping chamber. The diaphragm is then moved in the opposite direction in a pumping stroke to force the liquid out of the pumping chamber by pressurized drive fluid acting directly on the diaphragm.
In double diaphragm pumps in which two diaphragms are connected together, each diaphragm has, on one side, a pumping chamber and, on the other side, a drive fluid chamber. Air or other fluid under pressure is alternately introduced into and exhausted from each drive fluid chamber. A control valve directs the fluid under pressure into one drive fluid chamber, causing the associated diaphragm to move in a pumping stroke, while the connecting mechanism pulls the other diaphragm in a suction stroke and causes air in its associated drive fluid chamber to be exhausted. Then air under pressure is introduced into the other drive fluid chamber to move its diaphragm in a pumping stroke.
Double diaphragm pumps have conventionally used a connecting rod extending coaxially between the two diaphragms. In such arrangements, the drive fluid chambers of each pump section are adjacent to one another, and the pumping sections are spaced outwardly relative to one another.
The various uses to which such pumps are applied require widely varying pump speeds and operating characteristics. Furthermore, even within a single application, fluid characteristics such as viscosity or slurry concentration are subject to change during pump operation. Frequently, the operational speed or other characteristics of the pump must be changed in order to accommodate such changes in pumped fluid.
As is apparent from the foregoing, the need exists for a system in which information relating to pump speed and pumped fluid characteristics can be monitored, and such information can in turn be used to effect pump control.